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<title>dynamic_bitset&lt;Block, Allocator&gt;</title>
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<h1>dynamic_bitset&lt;Block, Allocator&gt;</h1>
<h2>Contents</h2>

<dl class="index">
<dt><a href="#description">Description</a></dt>
<dt><a href="#synopsis">Synopsis</a></dt>
<dt><a href="#definitions">Definitions</a></dt>
<dt><a href="#examples">Examples</a></dt>
<dt><a href="#rationale">Rationale</a></dt>
<dt><a href="#header-files">Header Files</a></dt>
<dt><a href="#template-parameters">Template Parameters</a></dt>
<dt><a href="#concepts-modeled">Concepts modeled</a></dt>

<dt><a href="#type-requirements">Type requirements</a></dt>
<dt><a href="#public-base-classes">Public base classes</a></dt>
<dt><a href="#nested-type-names">Nested type names</a></dt>
<dt><a href="#public-data-members">Public data members</a></dt>
<dt><a href="#constructors">Constructors</a></dt>
<dt><a href="#destructor">Destructor</a></dt>
<dt><a href="#member-functions">Member functions</a></dt>
<dt><a href="#non-member-functions">Non-member functions</a></dt>
<dt><a href="#exception-guarantees">Exception guarantees</a></dt>

<dt><a href="#changes-from-previous-ver"><b>Changes from previous version(s)</b></a></dt>
<dt><a href="#see-also">See also</a></dt>
<dt><a href="#acknowledgements">Acknowledgements</a></dt>
</dl>
<h3><a id="description">Description</a></h3>
<p>The <tt>dynamic_bitset</tt> class represents a set of bits. It
provides accesses to the value of individual bits via an
<tt>operator[]</tt> and provides all of the bitwise operators
that one can apply to builtin integers, such as
<tt>operator&amp;</tt> and <tt>operator&lt;&lt;</tt>. The number
of bits in the set is specified at runtime via a parameter to the
constructor of the <tt>dynamic_bitset</tt>.</p>

<p>The <tt>dynamic_bitset</tt> class is nearly identical to the
<a href=
"https://boost.org/sgi/stl/bitset.html"><tt>std::bitset</tt></a>
class. The difference is that the size of the
<tt>dynamic_bitset</tt> (the number of bits) is specified at
run-time during the construction of a <tt>dynamic_bitset</tt>
object, whereas the size of a <tt>std::bitset</tt> is specified
at compile-time through an integer template parameter.</p>

<p>The main problem that <tt>dynamic_bitset</tt> is designed to
solve is that of representing a subset of a finite set. Each bit
represents whether an element of the finite set is in the subset
or not. As such the bitwise operations of
<tt>dynamic_bitset</tt>, such as <tt>operator&amp;</tt> and
<tt>operator|</tt>, correspond to set operations, such as
intersection and union.</p>
<h3><a id ="synopsis">Synopsis</a></h3>
<pre>
namespace boost {

template &lt;typename Block, typename Allocator&gt;
class dynamic_bitset
{
public:
    typedef Block <a href="#block_type">block_type</a>;
    typedef Allocator <a href="#allocator_type">allocator_type</a>;
    typedef <i>implementation-defined</i> <a href="#size_type">size_type</a>;

    static const int <a href=
       "#bits_per_block">bits_per_block</a> = <i>implementation-defined</i>;
    static const size_type <a href=
          "#npos">npos</a> = <i>implementation-defined</i>;

    class <a href="#reference">reference</a>
    {
        void operator&amp;(); // not defined

    public:
        // An automatically generated copy constructor.

        reference&amp; operator=(bool value);
        reference&amp; operator=(const reference&amp; rhs);

        reference&amp; operator|=(bool value);
        reference&amp; operator&amp;=(bool value);
        reference&amp; operator^=(bool value);
        reference&amp; operator-=(bool value);

        bool operator~() const;
        operator bool() const;
        reference&amp; flip();
    };

    typedef bool <a href="#const_reference">const_reference</a>;

    <a href=
"#cons0">dynamic_bitset</a>();

    explicit <a href=
"#cons1">dynamic_bitset</a>(const Allocator&amp; alloc);

    explicit <a href=
"#cons2">dynamic_bitset</a>(size_type num_bits, unsigned long value = 0,
                            const Allocator&amp; alloc = Allocator());

    template &lt;typename CharT, typename Traits, typename Alloc&gt;
    explicit <a href=
"#cons3">dynamic_bitset</a>(const std::basic_string&lt;CharT, Traits, Alloc&gt;&amp; s,
        typename std::basic_string&lt;CharT, Traits, Alloc&gt;::size_type pos = 0,
        typename std::basic_string&lt;CharT, Traits, Alloc&gt;::size_type n = std::basic_string&lt;CharT, Traits, Alloc&gt;::npos,
        const Allocator&amp; alloc = Allocator());

    template &lt;typename BlockInputIterator&gt;
    <a href=
"#cons4">dynamic_bitset</a>(BlockInputIterator first, BlockInputIterator last,
                   const Allocator&amp; alloc = Allocator());

    <a href=
"#cons5">dynamic_bitset</a>(const dynamic_bitset&amp; b);

    <a href=
"#move-cons">dynamic_bitset</a>(dynamic_bitset&amp;&amp; b);

    void <a href="#swap">swap</a>(dynamic_bitset&amp; b);

    dynamic_bitset&amp; <a href=
"#assign">operator=</a>(const dynamic_bitset&amp; b);

    dynamic_bitset&amp; <a href=
"#move-assign">operator=</a>(dynamic_bitset&amp;&amp; b);

    allocator_type <a href="#get_allocator">get_allocator()</a> const;

    void <a href=
"#resize">resize</a>(size_type num_bits, bool value = false);
    void <a href="#clear">clear</a>();
    void <a href="#pop_back">pop_back</a>();
    void <a href="#push_back">push_back</a>(bool bit);
    void <a href="#append1">append</a>(Block block);

    template &lt;typename BlockInputIterator&gt;
    void <a href="#append2">append</a>(BlockInputIterator first, BlockInputIterator last);

    dynamic_bitset&amp; <a href="#op-and-assign">operator&amp;=</a>(const dynamic_bitset&amp; b);
    dynamic_bitset&amp; <a href="#op-or-assign">operator|=</a>(const dynamic_bitset&amp; b);
    dynamic_bitset&amp; <a href="#op-xor-assign">operator^=</a>(const dynamic_bitset&amp; b);
    dynamic_bitset&amp; <a href="#op-sub-assign">operator-=</a>(const dynamic_bitset&amp; b);
    dynamic_bitset&amp; <a href="#op-sl-assign">operator&lt;&lt;=</a>(size_type n);
    dynamic_bitset&amp; <a href="#op-sr-assign">operator&gt;&gt;=</a>(size_type n);
    dynamic_bitset <a href="#op-sl">operator&lt;&lt;</a>(size_type n) const;
    dynamic_bitset <a href="#op-sr">operator&gt;&gt;</a>(size_type n) const;

    dynamic_bitset&amp; <a href="#set3">set</a>(size_type n, size_type len, bool val);
    dynamic_bitset&amp; <a href="#set2">set</a>(size_type n, bool val = true);
    dynamic_bitset&amp; <a href="#set1">set</a>();
    dynamic_bitset&amp; <a href="#reset3">reset</a>(size_type n, size_type len);
    dynamic_bitset&amp; <a href="#reset2">reset</a>(size_type n);
    dynamic_bitset&amp; <a href="#reset1">reset</a>();
    dynamic_bitset&amp; <a href="#flip3">flip</a>(size_type n, size_type len);
    dynamic_bitset&amp; <a href="#flip2">flip</a>(size_type n);
    dynamic_bitset&amp; <a href="#flip1">flip</a>();
    reference <a href="#at">at</a>(size_type n);
    bool <a href="#const-at">at</a>(size_type n) const;
    bool <a href="#test">test</a>(size_type n) const;
    bool <a href="#test">test_set</a>(size_type n, bool val = true);
    bool <a href="#all">all</a>() const;
    bool <a href="#any">any</a>() const;
    bool <a href="#none">none</a>() const;
    dynamic_bitset <a href="#op-not">operator~</a>() const;
    size_type <a href="#count">count</a>() const noexcept;

    reference <a href="#bracket">operator[]</a>(size_type pos);
    bool <a href="#const-bracket">operator[]</a>(size_type pos) const;

    unsigned long <a href="#to_ulong">to_ulong</a>() const;

    size_type <a href="#size">size</a>() const noexcept;
    size_type <a href="#num_blocks">num_blocks</a>() const noexcept;
    size_type <a href="#max_size">max_size</a>() const noexcept;
    bool <a href="#empty">empty</a>() const noexcept;
    size_type <a href="#capacity">capacity</a>() const noexcept;
    void <a href="#reserve">reserve</a>(size_type num_bits);
    void <a href="#shrink_to_fit">shrink_to_fit</a>();

    bool <a href="#is_subset_of">is_subset_of</a>(const dynamic_bitset&amp; a) const;
    bool <a href="#is_proper_subset_of">is_proper_subset_of</a>(const dynamic_bitset&amp; a) const;
    bool <a href="#intersects">intersects</a>(const dynamic_bitset&amp; a) const;

    size_type <a href="#find_first">find_first</a>() const;
    size_type <a href="#find_next">find_next</a>(size_type pos) const;

};


template &lt;typename B, typename A&gt;
bool <a href=
"#op-equal">operator==</a>(const dynamic_bitset&lt;B, A&gt;&amp; a, const dynamic_bitset&lt;B, A&gt;&amp; b);

template &lt;typename Block, typename Allocator&gt;
bool <a href=
"#op-not-equal">operator!=</a>(const dynamic_bitset&lt;Block, Allocator&gt;&amp; a, const dynamic_bitset&lt;Block, Allocator&gt;&amp; b);

template &lt;typename B, typename A&gt;
bool <a href=
"#op-less">operator&lt;</a>(const dynamic_bitset&lt;B, A&gt;&amp; a, const dynamic_bitset&lt;B, A&gt;&amp; b);

template &lt;typename Block, typename Allocator&gt;
bool <a href=
"#op-less-equal">operator&lt;=</a>(const dynamic_bitset&lt;Block, Allocator&gt;&amp; a, const dynamic_bitset&lt;Block, Allocator&gt;&amp; b);

template &lt;typename Block, typename Allocator&gt;
bool <a href=
"#op-greater">operator&gt;</a>(const dynamic_bitset&lt;Block, Allocator&gt;&amp; a, const dynamic_bitset&lt;Block, Allocator&gt;&amp; b);

template &lt;typename Block, typename Allocator&gt;
bool <a href=
"#op-greater-equal">operator&gt;=</a>(const dynamic_bitset&lt;Block, Allocator&gt;&amp; a, const dynamic_bitset&lt;Block, Allocator&gt;&amp; b);

template &lt;typename Block, typename Allocator&gt;
dynamic_bitset&lt;Block, Allocator&gt;
<a href=
"#op-and">operator&amp;</a>(const dynamic_bitset&lt;Block, Allocator&gt;&amp; b1, const dynamic_bitset&lt;Block, Allocator&gt;&amp; b2);

template &lt;typename Block, typename Allocator&gt;
dynamic_bitset&lt;Block, Allocator&gt;
<a href=
"#op-or">operator|</a>(const dynamic_bitset&lt;Block, Allocator&gt;&amp; b1, const dynamic_bitset&lt;Block, Allocator&gt;&amp; b2);

template &lt;typename Block, typename Allocator&gt;
dynamic_bitset&lt;Block, Allocator&gt;
<a href=
"#op-xor">operator^</a>(const dynamic_bitset&lt;Block, Allocator&gt;&amp; b1, const dynamic_bitset&lt;Block, Allocator&gt;&amp; b2);

template &lt;typename Block, typename Allocator&gt;
dynamic_bitset&lt;Block, Allocator&gt;
<a href=
"#op-sub">operator-</a>(const dynamic_bitset&lt;Block, Allocator&gt;&amp; b1, const dynamic_bitset&lt;Block, Allocator&gt;&amp; b2);

template &lt;typename Block, typename Allocator, typename CharT, typename Alloc&gt;
void <a href=
"#to_string">to_string</a>(const dynamic_bitset&lt;Block, Allocator&gt;&amp; b,
          std::basic_string&lt;CharT, Alloc&gt;&amp; s);

template &lt;typename Block, typename Allocator, typename BlockOutputIterator&gt;
void <a href=
"#to_block_range">to_block_range</a>(const dynamic_bitset&lt;Block, Allocator&gt;&amp; b,
                    BlockOutputIterator result);

template &lt;typename CharT, typename Traits, typename Block, typename Allocator&gt;
std::basic_ostream&lt;CharT, Traits&gt;&amp;
<a href=
"#op-out">operator&lt;&lt;</a>(std::basic_ostream&lt;CharT, Traits&gt;&amp; os, const dynamic_bitset&lt;Block, Allocator&gt;&amp; b);

template &lt;typename CharT, typename Traits, typename Block, typename Allocator&gt;
std::basic_istream&lt;CharT, Traits&gt;&amp;
<a href=
"#op-in">operator&gt;&gt;</a>(std::basic_istream&lt;CharT, Traits&gt;&amp; is, dynamic_bitset&lt;Block, Allocator&gt;&amp; b);

} // namespace boost
</pre>

<h3><a id="definitions">Definitions</a></h3>

<p>Each bit represents either the Boolean value true or false (1
or 0). To <i>set</i> a bit is to assign it 1. To <i>clear</i> or
<i>reset</i> a bit is to assign it 0. To <i>flip</i> a bit is to
change the value to 1 if it was 0 and to 0 if it was 1. Each bit
has a non-negative <i>position</i>. A bitset <tt>x</tt> contains
<tt>x.size()</tt> bits, with each bit assigned a unique position
in the range <tt>[0,x.size())</tt>. The bit at position 0 is
called the <i>least significant bit</i> and the bit at position
<tt>size() - 1</tt> is the <i>most significant bit</i>. When
converting an instance of <tt>dynamic_bitset</tt> to or from an
unsigned long <tt>n</tt>, the bit at position <tt>i</tt> of the
bitset has the same value as <tt>(n &gt;&gt; i) &amp; 1</tt>.</p>

<h3><a id="examples">Examples</a></h3>

<p>
<a href="./example/example1.cpp">Example 1</a> (setting
and reading some bits)
</p>
<p>
<a href="./example/example2.cpp">Example 2</a> (creating
some bitsets from integers)
</p>

<p>
<a href="./example/example3.cpp">Example 3</a> (performing
input/output and some bitwise operations).
</p>


<h3><a id="rationale">Rationale</a></h3>
<p>
<tt>dynamic_bitset</tt> is not a <a href=
"https://boost.org/sgi/stl/Container.html">Container</a> and
does not provide iterators for the following reason:
</p>

<ul>
<li>A container with a proxy <tt>reference</tt> type can not
fulfill the container requirements as specified in the C++
standard (unless one resorts to strange iterator semantics).
<tt>std::vector&lt;bool&gt;</tt> has a proxy <tt>reference</tt>
type and does not fulfill the container requirements and as a
result has caused many problems. One common problem is when
people try to use iterators from <tt>std::vector&lt;bool&gt;</tt>
with a Standard algorithm such as <tt>std::search</tt>. The
<tt>std::search</tt> requirements say that the iterator must be a
<a href=
"https://boost.org/sgi/stl/ForwardIterator.html">Forward
Iterator</a>, but the <tt>std::vector&lt;bool&gt;::iterator</tt>
does not meet this requirement because of the proxy reference.
Depending on the implementation, they may or not be a compile
error or even a run-time error due to this misuse. For further
discussion of the problem see <i>Effective STL</i> by Scott
Meyers). So <tt>dynamic_bitset</tt> tries to avoid these problems
by not pretending to be a container.</li>
</ul>

<p>Some people prefer the name "toggle" to "flip". The name
"flip" was chosen because that is the name used in <a href=
"https://boost.org/sgi/stl/bitset.html"><tt>std::bitset</tt></a>.
In fact, most of the function names for <tt>dynamic_bitset</tt>
were chosen for this reason.</p>

<p><tt>dynamic_bitset</tt> does not throw exceptions when a
precondition is violated (as is done in <tt>std::bitset</tt>).
Instead <tt>assert</tt> is used. See the guidelines for <a href=
"http://www.boost.org/community/error_handling.html">Error and Exception Handling</a>
for the explanation.</p>

<h3><a id="header-files">Header Files</a></h3>

<p>The class <tt>dynamic_bitset</tt> is defined in the header <a
href=
"../../boost/dynamic_bitset.hpp">boost/dynamic_bitset.hpp</a>.
Also, there is a forward declaration for <tt>dynamic_bitset</tt>
in the header <a href=
"../../boost/dynamic_bitset_fwd.hpp">boost/dynamic_bitset_fwd.hpp</a>.</p>

<h3><a id="template-parameters">Template parameters</a></h3>

<table summary=
"Describes the meaning of the template parameters and lists their corresponding default arguments">
<tr>
<th>Parameter</th>
<th>Description</th>
<th>Default</th>
</tr>
<tr>
<td><tt>Block</tt></td>
<td>The integer type in which the bits are stored.</td>
<td><tt>unsigned long</tt></td>
</tr>
<tr>

<td><tt>Allocator</tt></td>
<td>The allocator type used for all internal memory management.</td>
<td><tt>std::allocator&lt;Block&gt;</tt></td>
</tr>
</table>
<h3><a id="concepts-modeled">Concepts Modeled</a></h3>
<a href=
"https://boost.org/sgi/stl/Assignable.html">Assignable</a>, <a
href=
"https://boost.org/sgi/stl/DefaultConstructible.html">Default
Constructible</a>, <a href=
"https://boost.org/sgi/stl/EqualityComparable.html">Equality
Comparable</a>, <a href=
"https://boost.org/sgi/stl/LessThanComparable.html">LessThan
Comparable</a>.

<h3><a id="type-requirements">Type requirements</a></h3>

<tt>Block</tt> is an unsigned integer type. <tt>Allocator</tt>
satisfies the Standard requirements for an allocator.

<h3><a id="public-base-classes">Public base classes</a></h3>

None.
<h3><a id="nested-type-names">Nested type names</a></h3>
<hr />

<pre>
<a id="reference">dynamic_bitset::reference</a>
</pre>

<p>A proxy class that acts as a reference to a single bit. It
contains an assignment operator, a conversion to <tt>bool</tt>,
an <tt>operator~</tt>, and a member function <tt>flip</tt>. It
exists only as a helper class for <tt>dynamic_bitset</tt>'s
<tt>operator[]</tt>. The following table describes the valid
operations on the <tt>reference</tt> type. Assume that <tt>b</tt>
is an instance of <tt>dynamic_bitset</tt>, <tt>i, j</tt> are of
<tt>size_type</tt> and in the range <tt>[0,b.size())</tt>. Also,
note that when we write <tt>b[i]</tt> we mean an object of type
<tt>reference</tt> that was initialized from <tt>b[i]</tt>. The
variable <tt>x</tt> is a <tt>bool</tt>.</p>

<table border="1" summary=
"Semantics of several expressions involving usage of dynamic_bitset::reference">
<tr>
<th>Expression</th>
<th>Semantics</th>
</tr>
<tr>
<td><tt>x = b[i]</tt></td>
<td>Assign the ith bit of <tt>b</tt> to <tt>x</tt>.</td>
</tr>
<tr>
<td><tt>(bool)b[i]</tt></td>
<td>Return the ith bit of <tt>b</tt>.</td>
</tr>
<tr>
<td><tt>b[i] = x</tt></td>
<td>Set the ith bit of <tt>b</tt> to the value of <tt>x</tt> and
return <tt>b[i]</tt>.</td>
</tr>
<tr>
<td><tt>b[i] |= x</tt></td>
<td>Or the ith bit of <tt>b</tt> with the value of <tt>x</tt> and
return <tt>b[i]</tt>.</td>
</tr>
<tr>
<td><tt>b[i] &amp;= x</tt></td>
<td>And the ith bit of <tt>b</tt> with the value of <tt>x</tt>
and return <tt>b[i]</tt>.</td>
</tr>

<tr>
<td><tt>b[i] ^= x</tt></td>
<td>Exclusive-Or the ith bit of <tt>b</tt> with the value of
<tt>x</tt> and return <tt>b[i]</tt>.</td>
</tr>

<tr>
<td><tt>b[i] -= x</tt></td>
<td>If <tt>x==true</tt>, clear the ith bit of <tt>b</tt>. Returns
<tt>b[i]</tt>.</td>
</tr>

<tr>
<td><tt>b[i] = b[j]</tt></td>
<td>Set the ith bit of <tt>b</tt> to the value of the jth bit of
<tt>b</tt> and return <tt>b[i]</tt>.</td>
</tr>

<tr>
<td><tt>b[i] |= b[j]</tt></td>
<td>Or the ith bit of <tt>b</tt> with the jth bit of <tt>b</tt>
and return <tt>b[i]</tt>.</td>
</tr>

<tr>
<td><tt>b[i] &amp;= b[j]</tt></td>
<td>And the ith bit of <tt>b</tt> with the jth bit of <tt>b</tt> and return <tt>b[i]</tt>.</td>
</tr>
<tr>
<td><tt>b[i] ^= b[j]</tt></td>
<td>Exclusive-Or the ith bit of <tt>b</tt> with the jth bit of <tt>b</tt> and return <tt>b[i]</tt>.</td>

</tr>
<tr>
<td><tt>b[i] -= b[j]</tt></td>
<td>If the jth bit of <tt>b</tt> is set, clear the ith bit of <tt>b</tt>. Returns <tt>b[i]</tt>.</td>
</tr>
<tr>
<td><tt>x = ~b[i]</tt></td>

<td>Assign the opposite of the ith bit of <tt>b</tt> to <tt>x</tt>.</td>
</tr>
<tr>
<td><tt>(bool)~b[i]</tt></td>
<td>Return the opposite of the ith bit of <tt>b</tt>.</td>
</tr>
<tr>

<td><tt>b[i].flip()</tt></td>
<td>Flip the ith bit of <tt>b</tt> and return <tt>b[i]</tt>.</td>
</tr>
</table>
<hr />
<pre>
<a id="const_reference">dynamic_bitset::const_reference</a>
</pre>
The type <tt>bool</tt>.

<pre>
<a id="size_type">dynamic_bitset::size_type</a>
</pre>
The unsigned integer type for representing the size of the bit set.

<pre>
<a id="block_type">dynamic_bitset::block_type</a>
</pre>
The same type as <tt>Block</tt>.

<pre>
<a id="allocator_type">dynamic_bitset::allocator_type;</a>
</pre>
The same type as <tt>Allocator</tt>.


<hr />
<h3><a id="public-data-members">Public data members</a></h3>

<pre>
<a id="bits_per_block">dynamic_bitset::bits_per_block</a>
</pre>
The number of bits the type <tt>Block</tt> uses to represent values,
excluding any padding bits. Numerically equal
to <tt>std::numeric_limits&lt;Block&gt;::digits</tt>.

<pre>
<a id="npos">dynamic_bitset::npos</a>
</pre>
The maximum value of <tt>size_type</tt>.

<hr />
<h3><a id="constructors">Constructors</a></h3>

<hr />
<pre>
<a id=
"cons0">dynamic_bitset</a>()
</pre>

<b>Effects:</b> Constructs a bitset of size zero. The allocator
for this bitset is a default-constructed object of type
<tt>Allocator</tt>.<br />
 <b>Postconditions:</b> <tt>this-&gt;size() == 0</tt>.<br />
 <b>Throws:</b> Nothing unless the default constructor of
<tt>Allocator</tt> throws an exception.<br />
 (Required by <a href=
"https://boost.org/sgi/stl/DefaultConstructible.html">Default
Constructible</a>.)

<hr />
<pre>
<a id=
"cons1">dynamic_bitset</a>(const Allocator&amp; alloc)
</pre>

<b>Effects:</b> Constructs a bitset of size zero. A copy of the
<tt>alloc</tt> object will be used in subsequent bitset
operations such as <tt>resize</tt> to allocate memory.<br />
 <b>Postconditions:</b> <tt>this-&gt;size() == 0</tt>.<br />
 <b>Throws:</b> nothing.

<hr />
<pre>
<a id="cons2">dynamic_bitset</a>(size_type num_bits,
               unsigned long value = 0,
               const Allocator&amp; alloc = Allocator())
</pre>

<b>Effects:</b> Constructs a bitset from an integer. The first
<tt>M</tt> bits are initialized to the corresponding bits in
<tt>value</tt> and all other bits, if any, to zero (where <tt>M =
min(num_bits, std::numeric_limits&lt;unsigned long&gt;::digits)</tt>). A copy of
the <tt>alloc</tt> object will be used in subsequent bitset
operations such as <tt>resize</tt> to allocate memory. Note that, e.g., the
following
<br /><br />
<tt>
dynamic_bitset b<>( 16, 7 );
</tt><br /><br />
will match the <a href="#cons4">constructor from an iterator range</a> (not this
one), but the underlying implementation will still "do the right thing" and
construct a bitset of 16 bits, from the value 7.
<br />
<b>Postconditions:</b>

<ul>
<li><tt>this-&gt;size() == num_bits</tt></li>

<li>For all <tt>i</tt> in the range <tt>[0,M)</tt>,
<tt>(*this)[i] == (value &gt;&gt; i) &amp; 1</tt>.</li>

<li>For all <tt>i</tt> in the range <tt>[M,num_bits)</tt>,
<tt>(*this)[i] == false</tt>.</li>
</ul>

<b>Throws:</b> An allocation error if memory is exhausted
(<tt>std::bad_alloc</tt> if
<tt>Allocator=std::allocator</tt>).<br />


<hr />
<pre>
<a id="cons5">dynamic_bitset</a>(const dynamic_bitset&amp; x)
</pre>

<b>Effects:</b> Constructs a bitset that is a copy of the bitset
<tt>x</tt>. The allocator for this bitset is a copy of the
allocator in <tt>x</tt>. <br />
 <b>Postconditions:</b> For all <tt>i</tt> in the range
<tt>[0,x.size())</tt>, <tt>(*this)[i] == x[i]</tt>.<br />
 <b>Throws:</b> An allocation error if memory is exhausted
(<tt>std::bad_alloc</tt> if
<tt>Allocator=std::allocator</tt>).<br />
 (Required by <a href=
"https://boost.org/sgi/stl/Assignable.html">Assignable</a>.)

<hr />
<pre>
<a id="move-cons">dynamic_bitset</a>(dynamic_bitset&amp;&amp; x)
</pre>

<b>Effects:</b> Constructs a bitset that is the same as the bitset
<tt>x</tt>, while using the resources from <tt>x</tt>. The allocator
for this bitset is moved from the allocator in <tt>x</tt>. <br />
 <b>Postconditions:</b> For all <tt>i</tt> in the range
<tt>[0,x.size())</tt>, <tt>(*this)[i] == x[i]</tt>.<br />
 <b>Throws:</b> An allocation error if memory is exhausted
(<tt>std::bad_alloc</tt> if
<tt>Allocator=std::allocator</tt>).

<hr />
<pre>
template &lt;typename BlockInputIterator&gt;
explicit
<a id=
"cons4">dynamic_bitset</a>(BlockInputIterator first, BlockInputIterator last,
               const Allocator&amp; alloc = Allocator());
</pre>

<b>Effects:</b>
<ul>
<li>
If this constructor is called with a type <tt>BlockInputIterator</tt> which
<i>is actually an integral type</i>, the library behaves as if the constructor
from <tt>unsigned long</tt> were called, with arguments
<tt>static_cast&lt;size_type&gt;(first), last and alloc</tt>, in that order.
<br /><br />
Example:
<pre>
// b is constructed as if by calling the constructor
//
//   dynamic_bitset(size_type num_bits,
//                  unsigned long value = 0,
//                  const Allocator&amp; alloc = Allocator())
//
// with arguments
//
//   static_cast&lt;dynamic_bitset&lt;unsigned short&gt;::size_type&gt;(8),
//   7,
//   Allocator()
//
dynamic_bitset&lt;unsigned short&gt; b(8, 7);
</pre><br />
<i>Note:</i><br/>
At the time of writing (October 2008) this is aligned with the
proposed resolution for <a href=
    "http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-defects.html#438">library
    issue 438</a>. That is a <em>post <tt>C++03</tt></em>
change, and is currently in the working paper for
<tt>C++0x</tt>. Informally speaking, the critical changes with
respect to <tt>C++03</tt> are the drop of a <tt>static_cast</tt>
on the second argument, and more leeway as to <em>when</em> the
templated constructor should have the same effect as the (size,
value) one: only when <tt>InputIterator</tt> is an integral
type, in <tt>C++03</tt>; when it is either an integral type or
any other type that the implementation might detect as
impossible to be an input iterator, with the proposed
resolution. For the purposes of <tt>dynamic_bitset</tt> we limit
ourselves to the first of these two changes.<br /><br />
</li>
<li>
<i>Otherwise</i> (<i>i.e.</i> if the template argument is not an
integral type), constructs&mdash;under the condition in the
<tt>requires</tt> clause&mdash;a bitset based on a range of
blocks. Let <tt>*first</tt> be block number 0, <tt>*++first</tt>
block number 1, etc. Block number <tt>b</tt> is used to
initialize the bits of the dynamic_bitset in the position range
<tt>[b*bits_per_block, (b+1)*bits_per_block)</tt>. For each
block number <tt>b</tt> with value <tt>bval</tt>, the bit
<tt>(bval &gt;&gt; i) &amp; 1</tt> corresponds to the bit at
position <tt>(b * bits_per_block + i)</tt> in the bitset (where
<tt>i</tt> goes through the range <tt>[0, bits_per_block)</tt>).
</li>
</ul>
<br />
<b>Requires:</b> <tt>BlockInputIterator</tt> must be either an
integral type or a model of <a href=
    "https://boost.org/sgi/stl/InputIterator.html">Input
    Iterator</a> whose <tt>value_type</tt> is the same type as
<tt>Block</tt>.<br /> <b>Throws:</b> An allocation error if
memory is exhausted (<tt>std::bad_alloc</tt> if
<tt>Allocator=std::allocator</tt>).<br />

<hr />
<pre>
template&lt;typename Char, typename Traits, typename Alloc&gt;
explicit
<a id="cons3">dynamic_bitset</a>(const <a href=
"https://boost.org/sgi/stl/basic_string.html">std::basic_string</a>&lt;Char,Traits,Alloc&gt;&amp; s,
               typename std::basic_string&lt;CharT, Traits, Alloc&gt;::size_type pos = 0,
               typename std::basic_string&lt;CharT, Traits, Alloc&gt;::size_type n = <a
 href=
"https://boost.org/sgi/stl/basic_string.html">std::basic_string</a>&lt;Char,Traits,Alloc&gt;::npos,
               const Allocator&amp; alloc = Allocator())
</pre>

<b>Precondition:</b> <tt>pos &lt;= s.size()</tt> and the
characters used to initialize the bits must be <tt>0</tt> or
<tt>1</tt>.<br />
 <b>Effects:</b> Constructs a bitset from a string of 0's and
1's. The first <tt>M</tt> bits are initialized to the
corresponding characters in <tt>s</tt>, where <tt>M =
min(s.size() - pos, n)</tt>. Note that the <i>highest</i>
character position in <tt>s</tt>, not the lowest, corresponds to
the least significant bit. That is, character position <tt>pos +
M - 1 - i</tt> corresponds to bit <tt>i</tt>. So, for example,
<tt>dynamic_bitset(string("1101"))</tt> is the same as
<tt>dynamic_bitset(13ul)</tt>.<br />
 <b>Throws:</b> an allocation error if memory is exhausted
(<tt>std::bad_alloc</tt> if <tt>Allocator=std::allocator</tt>).

<hr />
<h3><a id="destructor">Destructor</a></h3>

<hr />
<pre>
~dynamic_bitset()
</pre>

<b>Effects:</b> Releases the memory associated with this bitset
and destroys the bitset object itself.<br />
 <b>Throws:</b> nothing.

<hr />
<h3><a id="member-functions">Member Functions</a></h3>

<hr />
<pre>
void <a id="swap">swap</a>(dynamic_bitset&amp; b);
</pre>

<b>Effects:</b> The contents of this bitset and bitset <tt>b</tt>
are exchanged.<br />
<b>Postconditions:</b> This bitset is equal to the original
<tt>b</tt>, and <tt>b</tt> is equal to the previous version of
this bitset.<br />
<b>Throws:</b> nothing.

<hr />
<pre>
dynamic_bitset&amp; <a id=
"assign">operator=</a>(const dynamic_bitset&amp; x)
</pre>

<b>Effects:</b> This bitset becomes a copy of the bitset
<tt>x</tt>.<br />
 <b>Postconditions:</b> For all <tt>i</tt> in the range
<tt>[0,x.size())</tt>, <tt>(*this)[i] == x[i]</tt>.<br />
 <b>Returns:</b> <tt>*this</tt>.<br />
 <b>Throws:</b> nothing. <br />
(Required by <a href=
"https://boost.org/sgi/stl/Assignable.html">Assignable</a>.)

<hr />
<pre>
dynamic_bitset&amp; <a id=
"move-assign">operator=</a>(dynamic_bitset&amp;&amp; x)
</pre>

<b>Effects:</b> This bitset becomes the same as the bitset
<tt>x</tt>, while using the resources from <tt>x</tt>.<br />
 <b>Postconditions:</b> For all <tt>i</tt> in the range
<tt>[0,x.size())</tt>, <tt>(*this)[i] == x[i]</tt>.<br />
 <b>Returns:</b> <tt>*this</tt>.<br />
 <b>Throws:</b> An allocation error if memory is exhausted
(<tt>std::bad_alloc</tt> if <tt>Allocator=std::allocator</tt>).

<hr />
<pre>
allocator_type <a id="get_allocator">get_allocator()</a> const;
</pre>
 <b>Returns:</b> A copy of the allocator object used to construct <tt>*this</tt>.

<hr />
<pre>
void <a id=
"resize">resize</a>(size_type num_bits, bool value = false);
</pre>

<b>Effects:</b> Changes the number of bits of the bitset to
<tt>num_bits</tt>. If <tt>num_bits &gt; size()</tt> then the bits
in the range <tt>[0,size())</tt> remain the same, and the bits in
<tt>[size(),num_bits)</tt> are all set to <tt>value</tt>. If
<tt>num_bits &lt; size()</tt> then the bits in the range
<tt>[0,num_bits)</tt> stay the same (and the remaining bits are
discarded).<br />
 <b>Postconditions:</b> <tt>this-&gt;size() == num_bits</tt>.<br />
 <b>Throws:</b> An allocation error if memory is exhausted
(<tt>std::bad_alloc</tt> if
<tt>Allocator=std::allocator</tt>).<br />


<hr />
<pre>
void <a id="clear">clear</a>()
</pre>

<b>Effects:</b> The size of the bitset becomes zero.<br />
 <b>Throws:</b> nothing.

<hr />
<pre>
void <a id="pop_back">pop_back</a>();
</pre>

<b>Precondition:</b> <tt>!this-&gt;empty()</tt>.<br />
<b>Effects:</b> Decreases the size of the bitset by one.<br />
 <b>Throws:</b> nothing.

<hr />
<pre>
void <a id="push_back">push_back</a>(bool value);
</pre>

<b>Effects:</b> Increases the size of the bitset by one, and sets
the value of the new most-significant bit to <tt>value</tt>.<br />
 <b>Throws:</b> An allocation error if memory is exhausted
(<tt>std::bad_alloc</tt> if
<tt>Allocator=std::allocator</tt>).<br />


<hr />
<pre>
void <a id="append1">append</a>(Block value);
</pre>

<b>Effects:</b> Appends the bits in <tt>value</tt> to the bitset
(appends to the most-significant end). This increases the size of
the bitset by <tt>bits_per_block</tt>. Let <tt>s</tt> be the old
size of the bitset, then for <tt>i</tt> in the range
<tt>[0,bits_per_block)</tt>, the bit at position <tt>(s + i)</tt>
is set to <tt>((value &gt;&gt; i) &amp; 1)</tt>.<br />
 <b>Throws:</b> An allocation error if memory is exhausted
(<tt>std::bad_alloc</tt> if
<tt>Allocator=std::allocator</tt>).<br />


<hr />
<pre>
template &lt;typename BlockInputIterator&gt;
void <a id=
"append2">append</a>(BlockInputIterator first, BlockInputIterator last);
</pre>

<b>Effects:</b> This function provides the same end result as the
following code, but is typically more efficient.

<pre>
for (; first != last; ++first)
  append(*first);
</pre>

<b>Requires:</b> The <tt>BlockInputIterator</tt> type must be a
model of <a href=
"https://boost.org/sgi/stl/InputIterator.html">Input
Iterator</a> and the <tt>value_type</tt> must be the same type as
<tt>Block</tt>.<br />
 <b>Throws:</b> An allocation error if memory is exhausted
(<tt>std::bad_alloc</tt> if
<tt>Allocator=std::allocator</tt>).<br />


<hr />
<pre>
dynamic_bitset&amp; <a id=
"op-and-assign">operator&amp;=</a>(const dynamic_bitset&amp; rhs)
</pre>

<b>Requires:</b> <tt>this-&gt;size() == rhs.size()</tt>.<br />
 <b>Effects:</b> Bitwise-AND all the bits in <tt>rhs</tt> with
the bits in this bitset. This is equivalent to:

<pre>
for (size_type i = 0; i != this-&gt;size(); ++i)
  (*this)[i] = (*this)[i] &amp; rhs[i];
</pre>

<b>Returns:</b> <tt>*this</tt>.<br />
 <b>Throws:</b> nothing.

<hr />
<pre>
dynamic_bitset&amp; <a id=
"op-or-assign">operator|=</a>(const dynamic_bitset&amp; rhs)
</pre>

<b>Requires:</b> <tt>this-&gt;size() == rhs.size()</tt>.<br />
 <b>Effects:</b> Bitwise-OR's all the bits in <tt>rhs</tt> with
the bits in this bitset. This is equivalent to:

<pre>
for (size_type i = 0; i != this-&gt;size(); ++i)
  (*this)[i] = (*this)[i] | rhs[i];
</pre>

<b>Returns:</b> <tt>*this</tt>.<br />
 <b>Throws:</b> nothing.

<hr />
<pre>
dynamic_bitset&amp; <a id=
"op-xor-assign">operator^=</a>(const dynamic_bitset&amp; rhs)
</pre>

<b>Requires:</b> <tt>this-&gt;size() == rhs.size()</tt>.<br />
 <b>Effects:</b> Bitwise-XOR's all the bits in <tt>rhs</tt> with
the bits in this bitset. This is equivalent to:

<pre>
for (size_type i = 0; i != this-&gt;size(); ++i)
  (*this)[i] = (*this)[i] ^ rhs[i];
</pre>

<b>Returns:</b> <tt>*this</tt>.<br />
 <b>Throws:</b> nothing.

<hr />
<pre>
dynamic_bitset&amp; <a id=
"op-sub-assign">operator-=</a>(const dynamic_bitset&amp; rhs)
</pre>

<b>Requires:</b> <tt>this-&gt;size() == rhs.size()</tt>.<br />
 <b>Effects:</b> Computes the set difference of this bitset and
the <tt>rhs</tt> bitset. This is equivalent to:

<pre>
for (size_type i = 0; i != this-&gt;size(); ++i)
  (*this)[i] = (*this)[i] &amp;&amp; !rhs[i];
</pre>

<b>Returns:</b> <tt>*this</tt>.<br />
 <b>Throws:</b> nothing.

<hr />
<pre>
dynamic_bitset&amp; <a id=
"op-sl-assign">operator&lt;&lt;=</a>(size_type n)
</pre>

<b>Effects:</b> Shifts the bits in this bitset to the left by
<tt>n</tt> bits. For each bit in the bitset, the bit at position
pos takes on the previous value of the bit at position <tt>pos -
n</tt>, or zero if no such bit exists.<br />
 <b>Returns:</b> <tt>*this</tt>.<br />
 <b>Throws:</b> nothing.

<hr />
<pre>
dynamic_bitset&amp; <a id=
"op-sr-assign">operator&gt;&gt;=</a>(size_type n)
</pre>

<b>Effects:</b> Shifts the bits in this bitset to the right by
<tt>n</tt> bits. For each bit in the bitset, the bit at position
<tt>pos</tt> takes on the previous value of bit <tt>pos + n</tt>,
or zero if no such bit exists.<br />
 <b>Returns:</b> <tt>*this</tt>.<br />
 <b>Throws:</b> nothing.

<hr />
<pre>
dynamic_bitset <a id=
"op-sl">operator&lt;&lt;</a>(size_type n) const
</pre>

<b>Returns:</b> a copy of <tt>*this</tt> shifted to the left by
<tt>n</tt> bits. For each bit in the returned bitset, the bit at
position pos takes on the value of the bit at position <tt>pos -
n</tt> of this bitset, or zero if no such bit exists.<br />
 <b>Throws:</b> An allocation error if memory is exhausted
(<tt>std::bad_alloc</tt> if <tt>Allocator=std::allocator</tt>).

<hr />
<pre>
dynamic_bitset <a id=
"op-sr">operator&gt;&gt;</a>(size_type n) const
</pre>

<b>Returns:</b> a copy of <tt>*this</tt> shifted to the right by
<tt>n</tt> bits. For each bit in the returned bitset, the bit at
position pos takes on the value of the bit at position <tt>pos +
n</tt> of this bitset, or zero if no such bit exists.<br />
 <b>Throws:</b> An allocation error if memory is exhausted
(<tt>std::bad_alloc</tt> if <tt>Allocator=std::allocator</tt>).

<hr />
<pre>
dynamic_bitset&amp; <a id="set1">set</a>()
</pre>

<b>Effects:</b> Sets every bit in this bitset to 1.<br />
<b>Returns:</b> <tt>*this</tt><br />
<b>Throws:</b> nothing.

<hr />
<pre>
dynamic_bitset&amp; <a id="flip1">flip</a>()
</pre>

<b>Effects:</b> Flips the value of every bit in this bitset.<br />
<b>Returns:</b> <tt>*this</tt><br />
<b>Throws:</b> nothing.

<hr />
<pre>
dynamic_bitset <a id="op-not">operator~</a>() const
</pre>

<b>Returns:</b> a copy of <tt>*this</tt> with all of its bits
flipped.<br />
<b>Throws:</b> An allocation error if memory is exhausted
(<tt>std::bad_alloc</tt> if <tt>Allocator=std::allocator</tt>).

<hr />
<pre>
dynamic_bitset&amp; <a id="reset1">reset</a>()
</pre>

<b>Effects:</b> Clears every bit in this bitset.<br />
<b>Returns:</b> <tt>*this</tt><br />
<b>Throws:</b> nothing.

<hr />
<pre>
dynamic_bitset&amp; <a id=
"set3">set</a>(size_type n, size_type len, bool val);
</pre>

<b>Precondition:</b> <tt>n + len &lt; this-&gt;size()</tt>.<br />
<b>Effects:</b> Sets every bit indexed from <tt>n</tt> to
<tt>n + len - 1</tt> inclusively if <tt>val</tt> is <tt>true</tt>, and
clears them if <tt>val</tt> is <tt>false</tt>. <br />
<b>Returns:</b> <tt>*this</tt>

<hr />
<pre>
dynamic_bitset&amp; <a id=
"set2">set</a>(size_type n, bool val = true)
</pre>

<b>Precondition:</b> <tt>n &lt; this-&gt;size()</tt>.<br />
 <b>Effects:</b> Sets bit <tt>n</tt> if <tt>val</tt> is
<tt>true</tt>, and clears bit <tt>n</tt> if <tt>val</tt> is
<tt>false</tt>. <br />
 <b>Returns:</b> <tt>*this</tt>

<hr />
<pre>
dynamic_bitset&amp; <a id=
"reset3">reset</a>(size_type n, size_type len);
</pre>

<b>Precondition:</b> <tt>n + len &lt; this-&gt;size()</tt>.<br />
<b>Effects:</b> Clears every bit indexed from <tt>n</tt> to
<tt>n + len - 1</tt> inclusively.<br />
<b>Returns:</b> <tt>*this</tt>

<hr />
<pre>
dynamic_bitset&amp; <a id="reset2">reset</a>(size_type n)
</pre>

<b>Precondition:</b> <tt>n &lt; this-&gt;size()</tt>.<br />
<b>Effects:</b> Clears bit <tt>n</tt>.<br />
<b>Returns:</b> <tt>*this</tt>

<hr />
<pre>
dynamic_bitset&amp; <a id="flip3">flip</a>(size_type n, size_type len)
</pre>

<b>Precondition:</b> <tt>n + len &lt; this-&gt;size()</tt>.<br />
<b>Effects:</b> Flips every bit indexed from <tt>n</tt> to
<tt>n + len - 1</tt> inclusively.<br />
<b>Returns:</b> <tt>*this</tt>

<hr />
<pre>
dynamic_bitset&amp; <a id="flip2">flip</a>(size_type n)
</pre>

<b>Precondition:</b> <tt>n &lt; this-&gt;size()</tt>.<br />
<b>Effects:</b> Flips bit <tt>n</tt>.<br />
<b>Returns:</b> <tt>*this</tt>

<hr />
<pre>
size_type <a id="size">size</a>() const
</pre>

<b>Returns:</b> the number of bits in this bitset.<br />
<b>Throws:</b> nothing.

<hr />
<pre>
size_type <a id="num_blocks">num_blocks</a>() const
</pre>

<b>Returns:</b> the number of blocks in this bitset.<br />
<b>Throws:</b> nothing.

<hr />
<pre>
size_type <a id="max_size">max_size</a>() const;
</pre>

<b>Returns:</b> the maximum size of a <tt>dynamic_bitset</tt>
object having the same type as <tt>*this</tt>. Note that if
any <tt>dynamic_bitset</tt> operation causes <tt>size()</tt> to
exceed <tt>max_size()</tt> then the <i>behavior is undefined</i>.
<br /><br />[The semantics of this function could change slightly
when lib issue 197 will be closed]<br />

<hr />
<pre>
bool <a id="empty">empty</a>() const;
</pre>

<b>Returns:</b> <tt>true</tt> if <tt>this->size() == 0</tt>, <tt>false</tt>
otherwise. <i>Note</i>: not to be confused with <tt>none()</tt>, that has
different semantics.

<hr />
<pre>
size_type <a id="capacity">capacity</a>() const;
</pre>

<b>Returns:</b>  The total number of elements that <tt>*this</tt> can hold without requiring
reallocation.<br />
<b>Throws:</b> nothing.

<hr />
<pre>
void <a id="reserve">reserve</a>(size_type num_bits);
</pre>

<b>Effects:</b> A directive that informs the bitset of a planned change in size, so that it can
manage the storage allocation accordingly. After reserve(), capacity() is greater or equal to the
argument of reserve() if reallocation happens; and equal to the previous value of capacity() otherwise.
Reallocation happens at this point if and only if the current capacity is less than the argument of
reserve(). <br />
<i>Note:</i> It does not change the size() of the bitset.<br />
<b>Postcondtitions:</b> <tt>this->capacity() >= num_bits</tt>.<br />
<b>Throws:</b> An allocation error if memory is exhausted
(<tt>std::bad_alloc</tt> if <tt>Allocator=std::allocator</tt>).

<hr />
<pre>
void <a id="shrink_to_fit">shrink_to_fit</a>();
</pre>

<b>Effects:</b> shrink_to_fit() is a request to reduce memory use by removing unused capacity.<br />
<i>Note:</i> It does not change the size() of the bitset.<br />
<b>Throws:</b> An allocation error if memory is exhausted
(<tt>std::bad_alloc</tt> if <tt>Allocator=std::allocator</tt>).

<hr />
<pre>
size_type <a id="count">count</a>() const
</pre>

<b>Returns:</b> the number of bits in this bitset that are
set.<br />
<b>Throws:</b> nothing.

<hr />
<pre>
bool <a id="all">all</a>() const
</pre>

<b>Returns:</b> <tt>true</tt> if all bits in this bitset are set or
if <tt>size() == 0</tt>, and otherwise returns <tt>false</tt>.<br />
<b>Throws:</b> nothing.

<hr />
<pre>
bool <a id="any">any</a>() const
</pre>

<b>Returns:</b> <tt>true</tt> if any bits in this bitset are set,
and otherwise returns <tt>false</tt>.<br />
<b>Throws:</b> nothing.

<hr />
<pre>
bool <a id="none">none</a>() const
</pre>

<b>Returns:</b> <tt>true</tt> if no bits are set, and otherwise
returns <tt>false</tt>.<br />
<b>Throws:</b> nothing.

<hr />
<pre>
reference <a id="at">at</a>(size_type n)
</pre>

<b>Precondition:</b> <tt>n &lt; this-&gt;size()</tt>.<br />
<b>Returns:</b> The same as <tt>operator[](n)</tt>.<br />
<b>Throws:</b> <tt>std::out_of_range</tt> if that <tt>n</tt> is not within the range of the bitset.

<hr />
<pre>
bool <a id="const-at">at</a>(size_type n) const
</pre>

<b>Precondition:</b> <tt>n &lt; this-&gt;size()</tt>.<br />
<b>Returns:</b> The same as <tt>operator[](n)</tt>.<br />
<b>Throws:</b> <tt>std::out_of_range</tt> if that <tt>n</tt> is not within the range of the bitset.

<hr />
<pre>
bool <a id="test">test</a>(size_type n) const
</pre>

<b>Precondition:</b> <tt>n &lt; this-&gt;size()</tt>.<br />
 <b>Returns:</b> <tt>true</tt> if bit <tt>n</tt> is set and
<tt>false</tt> is bit <tt>n</tt> is 0.

<hr />
<pre>
bool <a id="test">test_set</a>(size_type n, bool val = true)
</pre>

<b>Precondition:</b> <tt>n &lt; this-&gt;size()</tt>.<br />
 <b>Effects:</b> Sets bit <tt>n</tt> if <tt>val</tt> is
<tt>true</tt>, and clears bit <tt>n</tt> if <tt>val</tt> is
<tt>false</tt>. <br />
 <b>Returns:</b> <tt>true</tt> if the previous state of bit
<tt>n</tt> was set and <tt>false</tt> is bit <tt>n</tt> is 0.

<hr />
<pre>
reference <a id="bracket">operator[]</a>(size_type n)
</pre>

<b>Precondition:</b> <tt>n &lt; this-&gt;size()</tt>.<br />
 <b>Returns:</b> a <tt>reference</tt> to bit <tt>n</tt>. Note
that <tt>reference</tt> is a proxy class with an assignment
operator and a conversion to <tt>bool</tt>, which allows you to
use <tt>operator[]</tt> for assignment. That is, you can write
both <tt>x = b[n]</tt> and <tt>b[n] = x</tt>. However, in many
other respects the proxy is not the same as the true reference
type <tt>bool&amp;</tt>.

<hr />
<pre>
bool <a id="const-bracket">operator[]</a>(size_type n) const
</pre>

<b>Precondition:</b> <tt>n &lt; this-&gt;size()</tt>.<br />
<b>Returns:</b> The same as <tt>test(n)</tt>.

<hr />
<pre>
unsigned long <a id="to_ulong">to_ulong</a>() const
</pre>

<b>Returns:</b> The numeric value corresponding to the bits in <tt>*this</tt>.
<br />
<b>Throws:</b> <tt>std::overflow_error</tt> if that value is too large to
be represented in an <tt>unsigned long</tt>, i.e. if <tt>*this</tt> has
any non-zero bit at a position <tt>&gt;=
std::numeric_limits&lt;unsigned long&gt;::digits</tt>.

<hr />
<pre>
bool <a id=
"is_subset_of">is_subset_of</a>(const dynamic_bitset&amp; a) const
</pre>

<b>Requires:</b> <tt>this-&gt;size() == a.size()</tt><br />
<b>Returns:</b> true if this bitset is a subset of bitset
<tt>a</tt>. That is, it returns true if, for every bit that is
set in this bitset, the corresponding bit in bitset <tt>a</tt> is
also set. Otherwise this function returns false.<br />
<b>Throws:</b> nothing.

<hr />
<pre>
bool <a id=
"is_proper_subset_of">is_proper_subset_of</a>(const dynamic_bitset&amp; a) const
</pre>

<b>Requires:</b> <tt>this-&gt;size() == a.size()</tt><br />
<b>Returns:</b> true if this bitset is a proper subset of bitset
<tt>a</tt>. That is, it returns true if, for every bit that is
set in this bitset, the corresponding bit in bitset <tt>a</tt> is
also set and if <tt>this-&gt;count() &lt; a.count()</tt>.
Otherwise this function returns false.<br />
<b>Throws:</b> nothing.

<hr />
<pre>
bool <a id=
"intersects">intersects</a>(const dynamic_bitset&amp; a) const
</pre>

<b>Requires:</b> <tt>this-&gt;size() == a.size()</tt><br />
<b>Returns:</b> true if this bitset and <tt>a</tt> intersect.
That is, it returns true if, there is a bit which is set in this
bitset, such that the corresponding bit in bitset <tt>a</tt> is
also set. Otherwise this function returns false.<br />
<b>Throws:</b> nothing.

<hr />
<pre>
size_type <a id = "find_first">find_first</a>() const;
</pre>

<b>Returns:</b> the lowest index <tt>i</tt> such as bit <tt>i</tt>
is set, or <tt>npos</tt> if <tt>*this</tt> has no on bits.

<hr />
<pre>
size_type <a id="find_next">find_next</a>(size_type pos) const;
</pre>

<b>Returns:</b> the lowest index <tt>i</tt> greater than
<tt>pos</tt> such as bit <tt>i</tt> is set, or <tt>npos</tt> if
no such index exists.

<hr />
<pre>
bool <a id=
"op-equal">operator==</a>(const dynamic_bitset&amp; rhs) const
</pre>

<b>Returns:</b> <tt>true</tt> if <tt>this-&gt;size() ==
rhs.size()</tt> and if for all <tt>i</tt> in the range
<tt>[0,rhs.size())</tt>, <tt>(*this)[i] == rhs[i]</tt>. Otherwise
returns <tt>false</tt>.<br />
 <b>Throws:</b> nothing.<br />
 (Required by <a href=
"https://boost.org/sgi/stl/EqualityComparable.html">Equality
Comparable</a>.)

<hr />
<pre>
bool <a id=
"op-not-equal">operator!=</a>(const dynamic_bitset&amp; rhs) const
</pre>

<b>Returns:</b> <tt>!((*this) == rhs)</tt><br />
<b>Throws:</b> nothing.<br />
(Required by <a href=
"https://boost.org/sgi/stl/EqualityComparable.html">Equality
Comparable</a>.)

<hr />
<pre>
bool <a id=
"op-less">operator&lt;</a>(const dynamic_bitset&amp; rhs) const
</pre>

<b>Returns:</b> <tt>true</tt> if this bitset is lexicographically
less than <tt>rhs</tt>, and returns <tt>false</tt> otherwise.
(See the description of <a href=
"https://boost.org/sgi/stl/lexicographical_compare.html">lexicographical_compare</a>
for a definition of lexicographic ordering). <br />
<b>Throws:</b> nothing.<br />
(Required by <a href=
"https://boost.org/sgi/stl/LessThanComparable.html">Less Than
Comparable</a>.)

<hr />
<pre>
bool <a id=
"op-greater">operator&gt;</a>(const dynamic_bitset&amp; rhs) const
</pre>

<b>Returns:</b> <tt>!((*this) &lt; rhs || (*this) ==
rhs)</tt><br />
<b>Throws:</b> nothing.<br />
(Required by <a href=
"https://boost.org/sgi/stl/LessThanComparable.html">Less Than
Comparable</a>.)

<hr />
<pre>
bool <a id=
"op-less-equal">operator&lt;=</a>(const dynamic_bitset&amp; rhs) const
</pre>

<b>Returns:</b> <tt>(*this) &lt; rhs || (*this) == rhs</tt><br />
<b>Throws:</b> nothing.<br />
(Required by <a href=
"https://boost.org/sgi/stl/LessThanComparable.html">Less Than
Comparable</a>.)

<hr />
<pre>
bool <a id=
"op-greater-equal">operator&gt;=</a>(const dynamic_bitset&amp; rhs) const
</pre>

<b>Returns:</b> <tt>(*this) &gt; rhs || (*this) == rhs</tt><br />
<b>Throws:</b> nothing.<br />
(Required by <a href=
"https://boost.org/sgi/stl/LessThanComparable.html">Less Than
Comparable</a>.)

<hr />
<h3><a id="non-member-functions">Non-Member Functions</a></h3>

<hr />
<pre>
dynamic_bitset <a id=
"op-and">operator&amp;</a>(const dynamic_bitset&amp; a, const dynamic_bitset&amp; b)
</pre>

<b>Requires:</b> <tt>a.size() == b.size()</tt><br />
<b>Returns:</b> A new bitset that is the bitwise-AND of the
bitsets <tt>a</tt> and <tt>b</tt>.<br />
<b>Throws:</b> An allocation error if memory is exhausted
(<tt>std::bad_alloc</tt> if <tt>Allocator=std::allocator</tt>).

<hr />
<pre>
dynamic_bitset <a id=
"op-or">operator|</a>(const dynamic_bitset&amp; a, const dynamic_bitset&amp; b)
</pre>

<b>Requires:</b> <tt>a.size() == b.size()</tt><br />
<b>Returns:</b> A new bitset that is the bitwise-OR of the
bitsets <tt>a</tt> and <tt>b</tt>.<br />
<b>Throws:</b> An allocation error if memory is exhausted
(<tt>std::bad_alloc</tt> if <tt>Allocator=std::allocator</tt>).

<hr />
<pre>
dynamic_bitset <a id=
"op-xor">operator^</a>(const dynamic_bitset&amp; a, const dynamic_bitset&amp; b)
</pre>

<b>Requires:</b> <tt>a.size() == b.size()</tt><br />
<b>Returns:</b> A new bitset that is the bitwise-XOR of the
bitsets <tt>a</tt> and <tt>b</tt>.<br />
<b>Throws:</b> An allocation error if memory is exhausted
(<tt>std::bad_alloc</tt> if <tt>Allocator=std::allocator</tt>).

<hr />
<pre>
dynamic_bitset <a id=
"op-sub">operator-</a>(const dynamic_bitset&amp; a, const dynamic_bitset&amp; b)
</pre>

<b>Requires:</b> <tt>a.size() == b.size()</tt><br />
<b>Returns:</b> A new bitset that is the set difference of the
bitsets <tt>a</tt> and <tt>b</tt>.<br />
<b>Throws:</b> An allocation error if memory is exhausted
(<tt>std::bad_alloc</tt> if <tt>Allocator=std::allocator</tt>).

<hr />
<pre>
template &lt;typename CharT, typename Alloc&gt;
void <a id=
"to_string">to_string</a>(const dynamic_bitset&lt;Block, Allocator&gt;&amp; b,
               <a href=
"https://boost.org/sgi/stl/basic_string.html">std::basic_string</a>&lt;Char,Traits,Alloc&gt;&amp; s)
</pre>

<b>Effects:</b> Copies a representation of <tt>b</tt> into the
string <tt>s</tt>. A character in the string is <tt>'1'</tt> if
the corresponding bit is set, and <tt>'0'</tt> if it is not.
Character position <tt>i</tt> in the string corresponds to bit
position <tt>b.size() - 1 - i</tt>. <br />
 <b>Throws:</b> If memory is exhausted, the string will throw an
allocation error.<br />
 <b>Rationale:</b> This function is not a member function taking
zero arguments and returning a string for a couple reasons.
First, this version can be slighly more efficient because the
string is not copied (due to being passed by value). Second, as a
member function, to allow for flexibility with regards to the
template parameters of <tt>basic_string</tt>, the member function
would require explicit template parameters. Few C++ programmers
are familiar with explicit template parameters, and some C++
compilers do not handle them properly.

<hr />
<pre>
template &lt;typename Block, typename Alloc, typename BlockOutputIterator&gt;
void <a id=
"to_block_range">to_block_range</a>(const dynamic_bitset&lt;Block, Alloc&gt;&amp; b, BlockOutputIterator result)
</pre>

<b>Effects:</b> Writes the bits of the bitset into the iterator
<tt>result</tt> a block at a time. The first block written
represents the bits in the position range
<tt>[0,bits_per_block)</tt> in the bitset, the second block
written the bits in the range
<tt>[bits_pre_block,2*bits_per_block)</tt>, and so on. For each
block <tt>bval</tt> written, the bit <tt>(bval &gt;&gt; i) &amp;
1</tt> corresponds to the bit at position <tt>(b * bits_per_block
+ i)</tt> in the bitset.<br />
 <b>Requires:</b> The type <tt>BlockOutputIterator</tt> must be a
model of <a href=
"https://boost.org/sgi/stl/OutputIterator.html">Output
Iterator</a> and its <tt>value_type</tt> must be the same type as
<tt>Block</tt>. Further, the size of the output range must be
greater or equal <tt>b.num_blocks()</tt>.

<hr />
<pre>
template &lt;typename BlockIterator, typename Block, typename Alloc&gt;
void <a id=
"from_block_range">from_block_range</a>(BlockIterator first,
    BlockIterator last, const dynamic_bitset&lt;Block, Alloc&gt;&amp; b)
</pre>

<b>Effects:</b> Reads blocks from the iterator range into the
bitset. <br />
 <b>Requires:</b> The type <tt>BlockIterator</tt> must be a model
of <a href="https://boost.org/sgi/stl/InputIterator.html">Input
Iterator</a> and its <tt>value_type</tt> must be the same type as
<tt>Block</tt>. The size of the iterator range must be less or
equal to <tt>b.num_blocks()</tt>.

<hr />
<pre>
template &lt;typename Char, typename Traits, typename Block, typename Alloc&gt;
basic_ostream&lt;Char, Traits&gt;&amp;
<a id=
"op-out">operator&lt;&lt;</a>(basic_ostream&lt;Char, Traits&gt;&amp; os, const dynamic_bitset&lt;Block, Alloc&gt;&amp; b)
</pre>

<b>Effects:</b> Inserts a textual representation of b into the stream
<tt>os</tt> (highest bit first). Informally, the output is the same as doing

<pre>
std::basic_string&lt;Char, Traits&gt; s;
boost::to_string(x, s):
os &lt;&lt; s;
</pre>

except that the stream inserter takes into accout the locale imbued into
<tt>os</tt>, which <tt>boost::to_string()</tt> can't do. Here is a more
precise specification, given in terms of "as if" rule: first, for each
valid position i into the bitset <tt>b</tt> let's put:

 <tt>character_of(b[i)]) = b[i]? os.widen('1') : os.widen('0');</tt>

Let also <tt>s</tt> be a <tt>std::basic_string&lt;Char, Traits&gt;</tt>
object, having length <tt>b.size()</tt> and such as, for each <tt>i</tt>
in <tt>[0, b.size())</tt>,

 <tt>s[i] is character_of(b[i])</tt>

Then, the output, the effects on <tt>os</tt> and the exception behavior
is the same as outputting the object <tt>s</tt> to <tt>os</tt> (same
width, same exception mask, same padding, same setstate() logic)
<br />
<b>Returns:</b> os <br />
<b>Throws:</b> <tt>std::ios_base::failure</tt> if there is a
problem writing to the stream.

<hr />
<pre>
template &lt;typename Char, typename Traits, typename Block, typename Alloc&gt;
std::basic_istream&lt;Char,Traits&gt;&amp;
<a id=
"op-in">operator&gt;&gt;</a>(std::basic_istream&lt;Char,Traits&gt;&amp; is, dynamic_bitset&lt;Block, Alloc&gt;&amp; b)
</pre>

<b>Effects:</b> Extracts a <tt>dynamic_bitset</tt> from an input stream.
<br /><br />
 <i>Definitions:</i><br /><br />
 Let <i>Tr</i> be the traits_type of <i>is</i>. Then:
 <ol>
 <li>
 A (non-eof) character <tt>c</tt> extracted from <tt>is</tt>
 is a <i>bitset digit</i> if and only if either Tr::eq(c, is.widen('0')) or
 Tr::eq(c, is.widen('1')) return true.
 </li>
 <li>If c is a bitset digit, it's <i>corresponding bit value</i> is 0 if
 Tr::eq(c, is.widen('0')) is true, 1 otherwise.
 </li>
 </ol>

The function begins by constructing a <tt>sentry</tt> object <tt>k</tt> as if <tt>k</tt>
were constructed by

 <tt>typename std::basic_istream&lt;Char, Traits&gt;::sentry k(is)</tt>.

If <tt>bool(k)</tt> is true, it calls <tt>b.clear()</tt>
then attempts to extract characters from <tt>is</tt>. For each character c
that is a <i>bitset digit</i> the <i>corresponding bit value</i> is
appended to the less significant end of <tt>b</tt> (appending may throw).
If <tt>is.width()</tt> is greater than zero and smaller than <tt>b.max_size()</tt>
then the maximum number <tt>n</tt> of bits appended is <tt>is.width()</tt>;
otherwise <tt>n</tt> = <tt>b.max_size()</tt>.

Unless the extractor is exited via an exception, characters are extracted (and
corresponding bits appended) until any of the following occurs:<br />

<ul>
<li> <tt>n</tt> bits are stored into the bitset;</li>
<li> end-of-file, or an error, occurs on the input sequence;</li>
<li> the next available input character isn't a bitset digit</li>
</ul>
<br /> If no exception caused the function to exit then <tt>is.width(0)</tt> is
     called, regardless of how many characters were actually extracted. The
     sentry object k is destroyed.
<br />
<br />If the function extracts no characters[???], it calls is.setstate(std::ios::failbit),
     which may throw <tt>std::ios_base::failure</tt>.


<br />------


<br />
<b>Throws:</b> An allocation error if memory is exhausted
(<tt>std::bad_alloc</tt> if <tt>Allocator=std::allocator</tt>).
A <tt>std::ios_base::failure</tt> if there is a problem reading
from the stream.

<hr />
<h3><a id="exception-guarantees">Exception guarantees</a></h3>

All of <tt>dynamic_bitset</tt> functions offer at least the basic
exception guarantee.

<hr />
<h3><a id="changes-from-previous-ver">Changes from previous version(s)</a></h3>

<h4><i>Changes in Boost 1.56.0</i></h4>
<ul>
<li>Support for C++11 move constructors.</li>
<li>Warning fixes on MSVC 2013.</li>
<li>Support for C++11 minimal allocators.</li>
<li>Add noexcept specifications.</li>
</ul>

<h4><i>Changes in Boost 1.37.0</i></h4>
<ul>
<li>The constructor from a block range implements a "do the right thing"
behavior, a la standard sequences.</li>
</ul>

<!-- Changes from Boost 1.31.0 -->
<h4><i>Changes from Boost 1.31.0</i></h4>
<ul>
<li>
The stream extractor has completely different semantics: as natural
for a dynamic structure, it now expands the bitset as needed during
extraction. The new behaviour mimics that of the <tt>basic_string</tt>
extractor but there are some differences the user should be aware of;
so, please, check the <a href="#op-in">documentation</a>. (One
difference concerns the case where <code>stream.width() &gt;
    bitset.max_size() &gt; 0</code>. In that circumstance the
extractor of <tt>dynamic_bitset</tt> never attempts to extract more
than <tt>max_size()</tt> characters, whereas the extractor of
<tt>basic_string</tt> goes on and, on conforming implementations,
eventually throws a <tt>length_error</tt> exception. Note: That's what
the standard mandates -see especially <a
    href="http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-defects.html#83">library
    issue 83</a>- but not all implementations conform)
<br /><br />
The stream extractor is now also "exception-aware" in the sense that
it works correctly when setting exception masks on the stream.
<br /><br />
</li>
<li>
Several member functions (<tt>empty()</tt>, <tt>find_first()</tt>
, <tt>find_next()</tt>, <tt>get_allocator()</tt>, <tt>intersects()</tt>
, <tt>max_size()</tt> <!--, <tt>reserve()</tt>, <tt>capacity()</tt> -->)
have been added.
</li>
<li>
The constructor from <tt>basic_string</tt> has a new parameter that was totally
forgotten before.
</li>

</ul>
<i>Technicalities and minor changes</i>
<ul>
<li>
The class <tt>reference</tt> has been reimplemented so that
dynamic_bitset's references behave more like references to standard
container elements. In particular it is now guaranteed that they
cannot be invalidated from a standard library swap() function
applied to their corresponding <tt>dynamic_bitset</tt>s.
</li>
</ul>
<i>General improvements</i>
<ul>
<li>
Several optimizations to member and non-member functions and to the
nested class <tt>reference</tt>.
</li>
</ul>

<hr />
<h3><a id="see-also">See also</a></h3>

<tt><a href=
"https://boost.org/sgi/stl/bitset.html">std::bitset</a></tt>,
<tt><a href=
"https://boost.org/sgi/stl/Vector.html">std::vector</a></tt>,

<h3><a id="acknowledgements">Acknowledgements</a></h3>

<p>We would like to thank the Boost community for putting in the
time to review and accept this library. This library is much
better than it ever would have been due to all the suggestions
from Boost members. We especially thank Matt Marcus for taking on
the task of review manager. Also, a special thanks goes to
James Kanze for his invaluable help with the internationalization
issues.</p>

<table summary="Copyright"> <tr> <td>Copyright &copy; 2001</td>
<td><a href="http://www.boost.org/people/jeremy_siek.htm">Jeremy
Siek</a>, Indiana University (<a
href="mailto:jsiek@osl.iu.edu">jsiek@osl.iu.edu</a>)<br /> <a
href="http://freshsources.com">Chuck Allison</a>, Senior Editor,
C/C++ Users Journal (<a
href="mailto:cda@freshsources.com">cda@freshsources.com</a>)<br
/></td> </tr> <tr>
<td>Copyright &copy; 2003-2004, 2008</td> <td><a
        href="http://gennaro-prota.50webs.com/">Gennaro Prota</a>
    (name.surname yahoo.com)</td>
</tr>
<tr>
<td>Copyright &copy; 2014</td>
<td>Ahmed Charles (<a href="mailto:acharles@outlook.com">acharles@outlook.com</a>)</td>
</tr>
<tr>
<td>Copyright &copy; 2014</td>
<td>Glen Fernandes (<a href="mailto:glenjofe@gmail.com">glenjofe@gmail.com</a>)</td>
</tr>
<tr>
<td>Copyright &copy; 2014</td>
<td>Riccardo Marcangelo (<a href="mailto:ricky.65@outlook.com">ricky.65@outlook.com</a>)</td>
</tr>
</table>
<br />
<div class="legalnotice">
    Distributed under the Boost Software License, Version 1.0.
    (See accompanying file <a href="../../LICENSE_1_0.txt">LICENSE_1_0.txt</a>
    or copy at <a class="ulink" href="http://www.boost.org/LICENSE_1_0.txt">
http://www.boost.org/LICENSE_1_0.txt</a>)
</div>


</div>
</div>
</div>
</div>
</div>
</div>
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